Although the present invention is described with reference to a fan module for a motor vehicle, it is not limited thereto, but can also be applied to other technical fields.
A fan module in a motor vehicle is used for thermal management. The fan module is generally provided on a radiator or heat exchanger in order to transport an air flow through the radiator and to thus ensure sufficient cooling, for example in stop-and-go traffic, if there is not a sufficient airstream.
A fan module typically comprises an externally driven fan or ventilator which usually conveys and compresses air by means of an impeller which rotates in a frame.
In order to ensure optimal utilisation of the radiator surface in substantially rectangular or non-square radiators, double-fan modules are sometimes used which comprise at least two fans. The structure and operation of such double-fan modules are for example described in DE 10 2004 034 733 A1, DE 10 2008 041 236 A1 and DE 102 57 838 A1.
A double-fan module often comprises one larger and one smaller fan. Furthermore, a fan frame is provided in most cases, in which the fans are mounted beside each other in a compact manner.
In parallel operation using both fans, in double-fan modules a higher level of noise generation may occur, and users usually find this unpleasant, which reduces the level of comfort. Two different designs are known to the applicant for the outflow region of the fans, and these have different effects on noise generation and air output.
A first design which is known to the applicant provides a completely open structure of the outflow region of the entire double-fan module. Therefore, the outflow is influenced as little as possible. However, in this case the outflows from the two fans may interfere with each other, and this may again result in undesired noise generation.
Another design which is known to the applicant provides that the outflow region of each individual fan of the double-fan module is completely surrounded, in a manner similar to a tube fan. By completely surrounding the fan, the air output (volume- or mass flow of the air) is reduced, however, since the outflow to the side is restricted.